The ratchet wrench has several advantages over the conventional closed or open end wrench. The fastener to be tightened or loosened is commonly in a confined location where a wrench has only a limited arc of motion when placed on the fastener. With an open end or a closed end wrench, the wrench must be removed from the fastener each time the limit of the arc of motion is reached and then repositioned. The ratchet wrench can be retained on the fastener with the ratcheting mechanism permitting the wrench to be readily returned to the initial point of motion without the wrench being removed from the fastener. When a reversible ratchet is provided, the wrench can be rotated freely in either direction as needed.
The ratchet wrench has in the past had one significant shortcoming relative to the closed or opened ended wrench. The wrench engaging surfaces of the fastener can often be a considerable distance from the end of the fastener, such as where the fastener is the common automotive spark plug where the wrench engaging surfaces lie along the length of the spark plug, or when a member, such as a bolt on which the fastener is secured, extends through the fastener. The conventional closed or opened end wrench can be simply slid over the end of the spark plug or bolt onto the wrench engaging surfaces of the fastener. The common ratchet wrench is provided with a square drive to engage a square aperture in a socket. The ability of the socket to contact the wrench surfaces on the fastener is therefore determined solely by the length of the socket. Long experience has shown that two different length socket sets are required for the majority of applications, including a so-called "short" socket set for use in tight areas and a so-called "deep" socket set for use with spark plugs, fasteners with through bolts, etc. This leads to great expense in necessitating the purchase of two complete socket sets. In addition, as the wrench handle is moved away from the fastener to permit the longer "deep" socket to be positioned between the wrench and fastener, the user must be careful to avoid applying a moment perpendicular the desired rotational direction to avoid overstressing the fastener.
Attempts have been made to eliminate the need for multiple length socket sets in ratchet wrench design by providing a ratchet wrench having a hole through the wrench and centered on the axis of rotation of the drive portion of the ratchet wrench. U.S. Pat. No. 125,695 to Sanborn, U.S. Pat. No. 1,165,995 to Mossberg and U.S. Pat. No. 2,317,461 all disclose a ratchet wrench with a through hole. The wrench in each of these patents is adapted for only a single fastener size. U.S. Pat. Nos. 1,347,691 to Forton and 2,300,479 to Wilson each disclose a ratchet wrench with a through hole which is adapted for using interchangable sockets to use the wrench with a range of fastener sizes. However, none of the wrenches disclosed in these patents permit the ratcheting direction to be reversed without turning over the wrench.
In ratchet wrenches adapted for use with a socket set, it is common to provide a spring loaded detent to secure the socket on the drive member of the wrench during use. In recent years, mechanisms have been developed for quick release of the socket from the wrench by retraction of the detent. Such mechanisms are described in U.S. Pat. Nos. 3,208,318 to Roberts and 3,532,013 to Haznar. These mechanisms, however, require a number of parts, which increase costs, and cannot be readily disassembled for repairs.
At the present time, no single ratchet wrench has been developed which incorporates the desired advantages noted above, including the presence of a through hole to eliminate the need of multiple sets of sockets and incorporating a quick release mechanism for the sockets used. A need therefore exists for such a socket wrench which is relatively uncomplicated in design and adaptable for inexpensive quantity production.